Devices are known for forming stacks of objects, such as printed materials. For example, newspapers are stacked and bundled for subsequent handling and transport.
As part of a typical operation, the objects are stacked in a stacker, on top of a turntable, to a desired quantity or height. Partial stacks may be rotated to equalize the height of the material in the stack. Once the final desired height is achieved, the completed stack is conveyed out of the stacker to a downstream operation, such as a strapping machine in which a strap is positioned around the stack for ease of handling.
In known stackers, the objects are introduced from above through a chute or other conveyance. A pair of parallel opposing moving walls are mounted on the turntable. The walls, often formed as belts, define lateral sides of the stacker. The walls move in the direction in which the stack is conveyed out of the stacker.
Four pushers are positioned on the walls to engage the edges of the stack and facilitate moving the stack out of the stacker. In such stackers, the pushers are positioned at each corner to engage the front and rear edges of the stack along both sides, in a symmetrical manner. As the walls move, the pushers, which also move in a symmetrical manner, push the stack from the stacker into the downstream process, e.g., a strapping machine.
The walls, which have a flattened oval profile, engage the sides of the stack throughout its movement through the stacker, and move in symmetrical, mirror image paths relative to one another. That is, if one wall moves in a clockwise direction, the opposite wall moves in a synchronous counterclockwise direction. One such stacker is described in Sjogren, U.S. Pat. No. 4,749,077, the disclosure of which is incorporated herein by reference.
One drawback to some known stackers is that the pushers are fixed relative to the moving walls. That is, the distance between the pushers as mounted to the walls is fixed. In order to change the size or dimension along the wall to, for example, accommodate materials of different sizes (widths), the pushers must be removed from the wall and remounted to the wall at the desired location or distance from one another. Alternatively, spacers are used to adjust the pusher locations on the walls. Such adjustments can be time consuming given that many such objects have different widths.
Another known stacker allows for adjusting the stacker to accommodate materials of different widths, but requires a complex mechanism with a substantial number of components and motors (or drives) to accomplish this adjustment.
With respect to the materials, typically, broadsheet type newspapers have a different width than tabloid type newspapers. And, one broadsheet may have a different width than other broadsheets. Thus, with each change in size of objects to be stacked, known stackers must be taken out of service and the pushers repositioned to match the size of the objects to be stacked.
Accordingly, there is a need for a stacker that allows for stacking and conveying objects of different sizes. Desirably, such a stacker can accommodate materials of different size without the need to take the stacker out of service to make such adjustments. More desirably still, such a stacker permits adjustment to be carried out as the stacker is operating or “on-the-fly”.